Recently, considerable research has been conducted regarding carbon nanotubes (CNTs) and CNT applications. One of the applications involves applying the CNTs to an electron emitter of a field emission device (FED). Typically, the FED applies an external electric field to a surface of the electron emitter so that electrons on the surface are emitted outward using quantum-mechanical tunneling. CNTs possess good conductivity, a good field enhancement effect, a lower work function than that of metal and good field emission properties. In addition, CNTs possess good chemical resistance properties and good mechanical strength, thus allowing for the manufacture of durable electron emitters.
A method of forming CNTs using Fe and Mo or Fe metal particles as catalysts by a thermal chemical vapor deposition (CVD) method is discussed in Chem. Phys. Lett. 292, 567 (1988) by J. Kong et al and in Chem. Phys. 296, 195 (1998) by J. Hafner et al. More recently, research on a method of forming CNTs on a cathode using various metal catalysts has been conducted. For example, a method of forming multi-walled CNTs on a tungsten tip using a nickel catalyst by a plasma-enhancement CVD method is described by S. H. Heo et al in Applied Phys. Lett. 90, 183109 (2007).
To use CNTs as a field emitter of the FED, it is necessary to form the CNTs around an apex of a cathode where an electric field is concentrated in order for the field emitter to be electrically reliable. Thus, the catalyst particles need to be formed around the apex of the cathode. One drawback is that, at present it is difficult to reliably control the catalyst particles.